A direct-recording printer is described which has printhead and a driven platen to advance the paper which at the same time provides counter-pressure to the printhead. A paper-cutting bar is provided having a cutting edge for cutting the paper. A paper compartment holds the paper supply, with the platen being accessible through the paper compartment for paper insertion. A cover for the paper compartment can be positioned either in the opened or closed positions.
Direct-recording printers of this type have been commercially available for some time. Such printers are, for example, categorized as lever (full character) printers, dot-matrix printers (ink-jet printers), but particularly as thermoprinters. All these printers require that the paper supply in the paper compartment be easily accessible, that reliable operation, in terms of the paper feed, be assured, and that, when cutting the paper, a clean cut point or cut line be defined. Normally, either paper stacked and folded in a Z-pattern (fan-folded) or paper rolls are utilized. It is particularly important that the paper compartment be easy to open, that the paper supply be easily replenished, and that, after replenishing, the paper web be easily aligned on the driven platen. It is also important that no difficulties arise between the printhead and the platen itself. Such difficulties can arise particularly in thermoprinters where a specific contact pressure prevails between the heating zone (printhead) of the thermoprinter and the platen.
Tests performed on a printer, by the assignee of the subject invention, in which the edge of the paper-cutting bar was mounted in close proximity to the surface of the platen demonstrated that there was a tendency for the paper web to become entangled around the platen. This occurred particularly after extended periods of printer non-use and is in all likelihood due to the deformation of the rolled paper. This is particularly problematic when the tangle occurs with a thermoprinter, since there the thermo head, as already noted, exerts substantial force on the platen, pressing down the paper. The increased temperature which arises after long use, along with this impact force, results in the above-mentioned paper deformation so that the undesired entanglement of the paper around the platen can occur when restarting the printer after some time.
A design in which the cover plate (lid) of the paper compartment would simply rotate when opening and closing would necessitate a space between the edge of the paper-cutting bar and the end of the cover plate. This space would result in contact between the paper and the platen and thus lead to the above-described negative entanglement effect.